Relationship between the biocontrol fungus Trichoderma harzianum and the phytopathogenic fungus Fusarium solani f.sp. pisi

• Relationship between Trichoderma harzianum and Fusarium solani was identified.
• Dual culture assay indicated that their growth was inhibited by each other.
• T. harzianum declined the population and root colonization of F. solani in soil.
• F. solani also reduced the population of T. harzianum and indigenous Trichoderma.
• The relationship between them was determined as a competitive growth inhibition.

Relationship between the biocontrol fungus Trichoderma harzianum ThzID1-M3 and the plant pathogen Fusarium solani f.sp. pisi (Fsp) was determined in this study. Dual culture assay indicated the competitive interaction between ThzID1-M3 and Fsp. Alginate pellets of ThzID1-M3 and Fsp conidia were added to non-sterile soil with pea seeds. The interaction between Trichoderma and Fsp adversely affected their establishment in soil. The addition of ThzID1-M3 significantly reduced the Fsp population, as well as the colonization of roots by Fsp. In contrast, the added Fsp significantly reduced the proliferation of ThzID1-M3 and Trichoderma spp. The results suggest that the competition may be the main mechanism of the antagonistic activity of Trichoderma against Fsp.